Such a room heating system is, for example, disclosed in the company brochure “Wireless regulation for floor heating” of Danfoss A/S, No. VD.78.K3.02, January 2002. The room thermostat measures the room temperature, and in dependence of the room temperature influences the floor heating system so that the temperature of the room air can be kept substantially constant.
The floor heating system can have different embodiments. Commonly known are, for example, floor heating systems working with a heat carrying medium, for example hot water. In this case, the regulating unit influences the flow of this heat carrying medium through the floor. The floor then acts as heat exchanger, which supplies the heat from the heat carrying medium to the room air.
In another embodiment, the floor heating system can work electrically. For this purpose, resistance heating elements are then inserted in the floor. The regulating device then influences the current, which flows through the resistance heating elements. Also in this case, the floor supplies the increased temperature, which is generated in the resistance heating elements by the flowing current, to the room air.
To many people a room heating via the floor is very comfortable. However, floor heating systems involve problems, which do not occur in connection with radiators. Depending on the nature of the floor used, it is important to have the floor temperature under control. When, for example, a wooden floor is concerned, the temperature must be limited to prevent a drying of the wood and a subsequent damaging of the floor. On the other hand, with a floor covered by tiles, stones or slabs, it is desired to keep a minimum temperature to avoid that a user gets “cold feet”.
To determine the floor temperature, a temperature sensor can be built into the floor. In many cases, a hollow space is provided, for example a pipe, in which the temperature sensor can be located. However, with such a location, some regulation problems occur. Due to the inertia of the floor, delays occur in the measuring, so that a regulation takes place too late, which causes an overshoot. Further, the position of the temperature sensor in the floor must be selected very carefully, as the future fitting up of the room can have an influence on the measured temperature. When, for example, a wardrobe is placed exactly over the temperature sensor, the wardrobe will reflect heat back to the floor, which influences the measuring of the floor temperature.